It is well known that dairy cows during specific periods of their life and/or under specific management or disease conditions face short periods, where they have an increased requirement for specific minerals such as calcium (Ca) and/or phosphorous (P) and/or potassium (K). For example, like sodium (Na), cattle need potassium (K) in large amounts to maintain normal body and organ function. Potassium works in conjunction with Na in the body to transport nutrients in and out of cells.
Potassium is the third most abundant mineral in the body and of major importance to the functioning of nerve cells and muscle cells. Hypokalemia may cause reduced gastro intestinal motility, reduced feed intake, reduced water intake, reduced body weight, dehydration, reduced milk yield and muscular weakness which may ultimately lead to recumbency.
As only little potassium storage occurs in the bovine body, potassium must be supplied daily in the diet. In cows off feed or with in-appetence therefore the reduced feed intake leads to reduced potassium supplementation, which may soon lead to hypokalemia.
Hypokalemia is particularly relevant for instance to fresh cows off feed and sick cows such as cows with displaced abomasum or other diseases causing the cow to become very sick and in-appetent or anorexic.
In order to avoid the above deficiencies the increased requirements for specific minerals are normally met with oral supplements of the single mineral in question. Such supplements are well known in the market, where they exist in the form of boluses or gels (calcium), boluses or drenches (phosphorous) or powders (potassium).
A preferred salt for the potassium supplement is potassium chloride, because of the high content of potassium in this salt, the very good solubility in water and the alkalizing effect of the chloride.
Since potassium chloride has a very unpleasant bitter tasting, usually the animals must be force-treated. In the case aqueous solutions are to be given, this may cause the potassium chloride to enter the lungs, which may be fatal to the animal. Furthermore, the use of a potassium containing gel results in dosage problems due to difficulties associated with the discharge of the gel from the container. In addition, also a gel provides the unpleasant taste. Using capsules containing potassium in powder form is also possible. However, the potassium content of such capsules is very low so that a considerable number of capsules must be given to the animal to be treated within relatively short intervals of time which is not practicable.
A preferred administration form is the solid bolus, since it is easy to administer, there is no waste and the risk of aspiration, whereby the product is drawn down the trachea, is significantly reduced. For a potassium supplement such as a potassium bolus the preferred amount of potassium is around 50 g per dose.
However, it is not possible today with any known technique to make solid boluses with a content of potassium chloride equal to or higher than approximately 40% (w/w). With such a low inclusion rate it is not possible to include the required content of potassium because the bolus becomes too big for the ruminant, e.g. a cow, to swallow. Consequently, there are no solid potassium boluses available in the market place today. Instead the products used are large gelatin capsules with pure potassium chloride, e.g. “C for Kalium” from the French company LPG.
In the prior art solid preparations having a high calcium content and which can be administered easily with precise dose adjustments are already known. For example, in the U.S. Pat. No. 5,395,622 it is described a method of providing dosage units containing calcium for administering to ruminants to treat hypocalcemia, said method comprising the steps of                (a) mixing CaCl2.xH2O and CaSO4.yH2O, x being a number greater than 0 and lower than 6 and y being a number equal to or greater than 0 and lower than or equal to 2, the weight ratio of CaCl2.xH2O to CaSO4.yH2O being from 1:0.05 to 1:2.4, to form a homogeneous mixture,        (b) adding water to said homogeneous mixture to provide a mass which will flow through a funnel having a neck diameter of 10 mm at 40° C., the amount of water not exceeding the amount needed to convert CaCl2.xH2O to CaCl2.6H2O and CaSO4.yH2O to CaSO4.2H2O9,        (c) introducing said mass into a plurality of casting moulds, and        (d) subjecting said mass contained in said moulds to a temperature such that said mass solidifies therein into a solid mass containing a mixture of CaCl2 and CaSO4 hydrates.        
Therefore, this calcium chloride containing preparation or calcium bolus is produced by solidification of a mixture of calcium chloride and calcium sulfate, which both exist in different hydration forms, i.e. both having different amounts of crystal water. By using such salts with low amounts of crystal water, adding a small amount of water and heating above the indicated temperature, where the crystal water is liberated, it is possible to get a liquid mass, which transforms into a solid mass, when it is cooled again. This product is also known under the trade name BOVIKALC®.
The same technique as disclosed in U.S. Pat. No. 5,395,622 cannot be used for making a potassium containing preparation or potassium bolus, since there are potassium salts such as potassium chloride that does not contain crystal water and therefore it is difficult to convert theses salts into the solid state again.
Further prior art is as follows:    Mueller F J et al. (Journal of the American College of Nutrition 1989, 8(5): 432) describe the effect of potassium supplementation by fertilization and potassium chloride bolus on mineral metabolism in lactating beef cows.    Sweeney R W (The Veterinary Clinics of North America. Food animal Practice November 1999, 15(3): 609-617) relates to the treatment of potassium disorders.    Peek S F et al. (Veterinary Therapeutics: Research in Applied Veterinary Medicine Fall 2000, 1(4): 235-244) is directed to hypokalemia, muscle weakness, and recumbency in diary cattle.    U.S. Pat. No. 4,976,963 deals with ruminant feed antacid containing potassium, sodium and chlorine.    FR Patent No. 2 851 423 discloses controlled diffusion ruminant feed bolus production, by mixing liquid and solid components and compression molding, useful for prolonged release of minerals, trace elements and vitamins.    CN Patent No. 102 550 832 relates to an animal feed additive and a preparation method thereof.    U.S. Pat. No. 5,958,464 describes a composition for preventing and treating milk fever in freshening cows, and a method of administering the composition.It is therefore an object of the present invention to avoid the disadvantages of prior art and to provide a solid and easily doseable preparation having a high potassium content (>40% (w/w)) which may be readily administered to ruminants.